THE MICROSCOPE. 
Vou. VI. DETROIT, OCTOBER 1886. No. 10. 
ORIGINAL COMMUNICATIONS. 
A SIMPLE FREEZING APPARATUS. 
BY FRANK W. BROWN, M. D., 
Professor of Histology and Microscopy, Detroit College of Medicine. 
FP XHOUGH the ordinary method of hardening a specimen in al- 
cohol and cutting at one’s leisure is much to be preferred, 
there are times when a rapid microscopical inspection is desired, 
or, what might be called an exploratory examination is to be made, 
to learn if an organ or other object be worthy of the slower and 
more thorough process, preparatory to a permanent mount. For 
sections that have been frozen, do not, as a rule, keep as well as 
those that have been hardened in alcohol, though they do equal 
service at the time of mounting. 
The most convenient method of freezing is by evaporation, 
and the agent generally employed for that purpose is sulphuric 
ether. 
Within the last few months’a company has begun the manu- 
facture of a liquid, the principal use of which is as a disinfectant. 
It was invented by M. Raoul Pictet, of Geneva, Switzerland, and is 
said to be composed of sulphurous anhydride (SO,) and carbon- 
ous anhydride (CO,). These gases are mixed and then cooled, and 
subjected to great pressure, sufficient to condense them to a, liquid 
form. This liquid is then stored in ordinary siphon bottles for 
convenience in handling, and placed on the market. 
Liberated slowly from the siphon it appears as a gas, when 
quickly, as aliquid. Relieved from the pressure, the liquid evap- 
orates very rapidly, thus producing an intense cold on any sur- 
face to which it may be applied. Mercury is frozen by it in a 
very short space of time, and the skin can be made quite “ solid ” 
in from five to ten seconds. 
